This invention relates to a valve actuation device for multi-valve type engines and more particularly to an improved valve actuating device for such engines that provides a compact cylinder head configuration.
It has been known that the performance of an internal combustion engine can be significantly improved by using multiple valves for each cylinder of the engine. The use of multiple valves permits a greater power output for the engine because multiple valves can provide the same effective flow area with lower inertias. For this reason, four valve per cylinder engines are quite common. The performance of an engine can be improved even further by utilizing more than two valves for either the intake and/or exhaust functions. However, as the number of valves increase, there is a difficulty in providing both a compact combustion chamber and one which has a relatively small surface area. Compact combustion chambers are desirable in order to maintain high compression ratios and small surface areas are required so as to prevent undue quenching. In addition, it is the normal practice to employ separate camshafts for driving the intake and exhaust valves. Where multiple camshafts and multiple valves are employed, the overall height and width of the engine can become quite large with conventional constructions.
There is shown in U.S. Letters Patents 4,624,222, issued Nov. 25, 1986, entitled "Intake Valve Structure For Internal Combustion Engine," issued in the name of Masaaki Yoshikawa, and assigned to the assignee of this application, an arrangement wherein a desired combustion chamber configuration can be enjoyed with multiple valves. In conjunction with the arrangement shown in that patent, there are provided three intake valves, two of which reciprocate about axes that lie in a common plane and the third of which reciprocates about an axis that is inclined to this plane. However, the axes intersect along a common line, which line coincides with the rotational axis of the actuating camshaft. Although this arrangement has numerous advantages, the camshaft tends to be relatively highly placed in the cylinder head and this can result in a higher engine height than is desirable. By canting the valves at a greater angle, the camshaft can be lowered but then the width of the engine will increase and the shape of the combustion chamber will not be as advantageous.
It is, therefore, a principal object of this invention to provide an improved arrangement for operating multiple valves of an internal combustion engine.
It is a further object of this invention to provide a valve actuating mechanism employing a camshaft wherein the camshaft is placed relatively low in the cylinder head so as to provide a low engine height and wherein the width of the cylinder head is not increased.